1. Field of the Invention
The present invention relates to systems and methods for protecting vehicle occupants from injury. More specifically, the present invention relates to a retention apparatus for keeping an airbag cushion in a stowed configuration until deployment.
2. Description of Related Art
The inclusion of inflatable safety restraint devices, or airbags, is now a legal requirement for many new vehicles. Airbags are typically installed in the steering wheel and in the dashboard on the passenger side of a car. Additionally, airbags may be installed to inflate beside the passenger to provide side impact protection, in front of the knees to protect the knees from impact, or at other strategic locations.
In the event of an accident, a sensor system within the vehicle senses an impact situation and triggers the ignition of an inflator. Inflation gases from the inflator fill the airbag cushions, which immediately inflate to protect the driver and/or passengers from impact against the interior surfaces of the vehicle. During normal vehicle operation, airbags are typically stowed behind covers to protect them from tampering and provide a more attractive interior facade for the vehicle. A number of different airbag types are in use, including frontal driver's side and passenger's side airbags, inflatable curtains, overhead airbags, and knee bolsters.
Often, an airbag cushion is covered with a fabric or polymer wrap designed to keep the cushion folded until the time the cushion deploys. Such a wrap may facilitate installation of the cushion in a vehicle, and also ensure that the cushion remains properly folded to deploy in the intended manner. In the case of an inflatable curtain, the wrap may be an elongated, tubular design. Many known wraps have perforations designed to permit the wrap to tear to permit emergence of the inflating cushion.
Unfortunately, such perforations must generally be formed with considerable precision to ensure that the wrap is strong enough to remain intact during further fabrication, shipping, and installation, and yet weak enough at the perforation to permit the wrap tear during deployment. If the wrap does not tear properly along the perforation during deployment, the cushion may fail to inflate in the proper manner. Consequently, it is important that the geometry of the perforation be tightly controlled. As a result, the tolerances of the perforations tend to be relatively tight, and the perforations are difficult to form with economical techniques.
Furthermore, many known wrap designs are difficult to place around the cushion. Some wraps, particularly those designed for elongated cushions such as inflatable curtain cushions, present assembly challenges because the cushion must be inserted lengthwise into the wrap. In some instances, relatively elaborate or labor intensive methods must be used to align the cushion with the wrap and then pull the cushion into the wrap. Some wraps can be improperly assembled with the corresponding cushion.
The time required to form a perforated wrap and place the wrap around the cushion adds significantly to the time required to produce the airbag module. Furthermore, such challenges and/or disadvantages also add to the cost of the module, thereby decreasing the availability and use of such airbag modules.